Photographic processing apparatus will typically comprise a developing section, a fixing section, a wash section and a dryer. The process liquids for the developing section and the fixer section are typically provided in containers which can be in the form of rigid moulded polyethylene containers, or collapsible containers consisting of a collapsible plastic cube insert within a corrugated board outer support.
After a process liquid has been used, but it is not yet fully exhausted, it is desirable to store the liquid for later further use. Thus when the apparatus is not in use, for example over-night, the process liquid is returned to its container. There is therefore a need for a cap assembly for the container which enables both the removal of liquid therefrom and the return of liquid thereto. Furthermore, a processing apparatus may operate according to a regime where process liquid is constantly recirculated through a processing cell, the recirculation loop including the container. Such a regime also demands the use of a cap assembly for the container which enables both the removal and return of liquid.
A storage container cap assembly is known comprising a body, means carried on said body for releasably connecting the cap assembly to an upwardly facing mouth of a collapsible storage container filled with process liquid, an outlet passage passing through the cap body to enable process liquid to be withdrawn from the storage container, and a downwardly directed inlet passage passing through the cap body to enable process liquid to be returned to the storage container.
Such a cap assembly has the disadvantage that process liquid returning to the container tends to collect at the top of the container, i.e. is it is not well mixed with the remainder of the process liquid in the container. Consequently, the process liquid which is returned to the processing apparatus tends to be chemically more depleted than the average process liquid in the container. This phenomena is more noticeable if the temperature of the process liquid increases in the processing apparatus. Warm returning process liquid tends to settle on top of the cooler liquid remaining in the container.
It is desirable that the container filled with process liquid is a collapsible container, that is its volume decreases as process liquid is withdrawn therefrom. The use of such containers has the advantage that air space within the container is maintained at a minimum level, thereby reducing evaporation, oxidation or other contamination of the liquid. The use of such collapsible containers however prevents the use of a cap assembly in which the inlet passage is extended so as to open adjacent the bottom of the container.